/**
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.hbase.regionserver.handler;
import java.io.IOException;
import java.util.concurrent.atomic.AtomicBoolean;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.hbase.HRegionInfo;
import org.apache.hadoop.hbase.HTableDescriptor;
import org.apache.hadoop.hbase.Server;
import org.apache.hadoop.hbase.executor.EventHandler;
import org.apache.hadoop.hbase.executor.EventType;
import org.apache.hadoop.hbase.regionserver.HRegion;
import org.apache.hadoop.hbase.regionserver.RegionServerAccounting;
import org.apache.hadoop.hbase.regionserver.RegionServerServices;
import org.apache.hadoop.hbase.util.CancelableProgressable;
import org.apache.hadoop.hbase.zookeeper.ZKAssign;
import org.apache.zookeeper.KeeperException;
/**
* Handles opening of a region on a region server.
* <p>
* This is executed after receiving an OPEN RPC from the master or client.
*/
@InterfaceAudience.Private
public class OpenRegionHandler extends EventHandler {
private static final Log LOG = LogFactory.getLog(OpenRegionHandler.class);
protected final RegionServerServices rsServices;
private final HRegionInfo regionInfo;
private final HTableDescriptor htd;
// We get version of our znode at start of open process and monitor it across
// the total open. We'll fail the open if someone hijacks our znode; we can
// tell this has happened if version is not as expected.
private volatile int version = -1;
//version of the offline node that was set by the master
private volatile int versionOfOfflineNode = -1;
public OpenRegionHandler(final Server server,
final RegionServerServices rsServices, HRegionInfo regionInfo,
HTableDescriptor htd) {
this(server, rsServices, regionInfo, htd, EventType.M_RS_OPEN_REGION, -1);
}
public OpenRegionHandler(final Server server,
final RegionServerServices rsServices, HRegionInfo regionInfo,
HTableDescriptor htd, int versionOfOfflineNode) {
this(server, rsServices, regionInfo, htd, EventType.M_RS_OPEN_REGION,
versionOfOfflineNode);
}
protected OpenRegionHandler(final Server server,
final RegionServerServices rsServices, final HRegionInfo regionInfo,
final HTableDescriptor htd, EventType eventType,
final int versionOfOfflineNode) {
super(server, eventType);
this.rsServices = rsServices;
this.regionInfo = regionInfo;
this.htd = htd;
this.versionOfOfflineNode = versionOfOfflineNode;
}
public HRegionInfo getRegionInfo() {
return regionInfo;
}
@Override
public void process() throws IOException {
boolean openSuccessful = false;
boolean transitionedToOpening = false;
final String regionName = regionInfo.getRegionNameAsString();
HRegion region = null;
try {
if (this.server.isStopped() || this.rsServices.isStopping()) {
return;
}
final String encodedName = regionInfo.getEncodedName();
// 3 different difficult situations can occur
// 1) The opening was cancelled. This is an expected situation
// 2) The region was hijacked, we no longer have the znode
// 3) The region is now marked as online while we're suppose to open. This would be a bug.
// Check that this region is not already online
if (this.rsServices.getFromOnlineRegions(encodedName) != null) {
LOG.error("Region " + encodedName +
" was already online when we started processing the opening. " +
"Marking this new attempt as failed");
return;
}
// Check that we're still supposed to open the region and transition.
// If fails, just return. Someone stole the region from under us.
// Calling transitionZookeeperOfflineToOpening initializes this.version.
if (!isRegionStillOpening()){
LOG.error("Region " + encodedName + " opening cancelled");
return;
}
if (!transitionZookeeperOfflineToOpening(encodedName, versionOfOfflineNode)) {
LOG.warn("Region was hijacked? Opening cancelled for encodedName=" + encodedName);
// This is a desperate attempt: the znode is unlikely to be ours. But we can't do more.
return;
}
transitionedToOpening = true;
// Open region. After a successful open, failures in subsequent
// processing needs to do a close as part of cleanup.
region = openRegion();
if (region == null) {
return;
}
boolean failed = true;
if (tickleOpening("post_region_open")) {
if (updateMeta(region)) {
failed = false;
}
}
if (failed || this.server.isStopped() ||
this.rsServices.isStopping()) {
return;
}
if (!isRegionStillOpening() || !transitionToOpened(region)) {
// If we fail to transition to opened, it's because of one of two cases:
// (a) we lost our ZK lease
// OR (b) someone else opened the region before us
// OR (c) someone cancelled the open
// In all cases, we try to transition to failed_open to be safe.
return;
}
// We have a znode in the opened state now. We can't really delete it as the master job.
// Transitioning to failed open would create a race condition if the master has already
// acted the transition to opened.
// Cancelling the open is dangerous, because we would have a state where the master thinks
// the region is opened while the region is actually closed. It is a dangerous state
// to be in. For this reason, from now on, we're not going back. There is a message in the
// finally close to let the admin knows where we stand.
// Successful region open, and add it to OnlineRegions
this.rsServices.addToOnlineRegions(region);
openSuccessful = true;
// Done! Successful region open
LOG.debug("Opened " + regionName + " on server:" +
this.server.getServerName());
} finally {
// Do all clean up here
if (!openSuccessful) {
doCleanUpOnFailedOpen(region, transitionedToOpening);
}
final Boolean current = this.rsServices.getRegionsInTransitionInRS().
remove(this.regionInfo.getEncodedNameAsBytes());
// Let's check if we have met a race condition on open cancellation....
// A better solution would be to not have any race condition.
// this.rsServices.getRegionsInTransitionInRS().remove(
// this.regionInfo.getEncodedNameAsBytes(), Boolean.TRUE);
// would help, but we would still have a consistency issue to manage with
// 1) this.rsServices.addToOnlineRegions(region);
// 2) the ZK state.
if (openSuccessful) {
if (current == null) { // Should NEVER happen, but let's be paranoid.
LOG.error("Bad state: we've just opened a region that was NOT in transition. Region="
+ regionName);
} else if (Boolean.FALSE.equals(current)) { // Can happen, if we're
// really unlucky.
LOG.error("Race condition: we've finished to open a region, while a close was requested "
+ " on region=" + regionName + ". It can be a critical error, as a region that"
+ " should be closed is now opened.");
}
}
}
}
private void doCleanUpOnFailedOpen(HRegion region, boolean transitionedToOpening)
throws IOException {
if (transitionedToOpening) {
try {
if (region != null) {
cleanupFailedOpen(region);
}
} finally {
// Even if cleanupFailed open fails we need to do this transition
// See HBASE-7698
tryTransitionFromOpeningToFailedOpen(regionInfo);
}
} else {
// If still transition to OPENING is not done, we need to transition znode
// to FAILED_OPEN
tryTransitionFromOfflineToFailedOpen(this.rsServices, regionInfo, versionOfOfflineNode);
}
}
/**
* Update ZK or META. This can take a while if for example the
* .META. is not available -- if server hosting .META. crashed and we are
* waiting on it to come back -- so run in a thread and keep updating znode
* state meantime so master doesn't timeout our region-in-transition.
* Caller must cleanup region if this fails.
*/
boolean updateMeta(final HRegion r) {
if (this.server.isStopped() || this.rsServices.isStopping()) {
return false;
}
// Object we do wait/notify on. Make it boolean. If set, we're done.
// Else, wait.
final AtomicBoolean signaller = new AtomicBoolean(false);
PostOpenDeployTasksThread t = new PostOpenDeployTasksThread(r,
this.server, this.rsServices, signaller);
t.start();
boolean tomActivated = this.server.getConfiguration().
getBoolean("hbase.assignment.timeout.management", false);
int assignmentTimeout = this.server.getConfiguration().
getInt("hbase.master.assignment.timeoutmonitor.period", 10000);
// Total timeout for meta edit. If we fail adding the edit then close out
// the region and let it be assigned elsewhere.
long timeout = assignmentTimeout * 10;
long now = System.currentTimeMillis();
long endTime = now + timeout;
// Let our period at which we update OPENING state to be be 1/3rd of the
// regions-in-transition timeout period.
long period = Math.max(1, assignmentTimeout/ 3);
long lastUpdate = now;
boolean tickleOpening = true;
while (!signaller.get() && t.isAlive() && !this.server.isStopped() &&
!this.rsServices.isStopping() && (endTime > now)) {
if (tomActivated) {
long elapsed = now - lastUpdate;
if (elapsed > period) {
// Only tickle OPENING if postOpenDeployTasks is taking some time.
lastUpdate = now;
tickleOpening = tickleOpening("post_open_deploy");
}
}
synchronized (signaller) {
try {
signaller.wait(period);
} catch (InterruptedException e) {
// Go to the loop check.
}
}
now = System.currentTimeMillis();
}
// Is thread still alive? We may have left above loop because server is
// stopping or we timed out the edit. Is so, interrupt it.
if (t.isAlive()) {
if (!signaller.get()) {
// Thread still running; interrupt
LOG.debug("Interrupting thread " + t);
t.interrupt();
}
try {
t.join();
} catch (InterruptedException ie) {
LOG.warn("Interrupted joining " +
r.getRegionInfo().getRegionNameAsString(), ie);
Thread.currentThread().interrupt();
}
}
// Was there an exception opening the region? This should trigger on
// InterruptedException too. If so, we failed. Even if tickle opening fails
// then it is a failure.
return ((!Thread.interrupted() && t.getException() == null) && tickleOpening);
}
/**
* Thread to run region post open tasks. Call {@link #getException()} after
* the thread finishes to check for exceptions running
* {@link RegionServerServices#postOpenDeployTasks(
* HRegion, org.apache.hadoop.hbase.catalog.CatalogTracker, boolean)}
* .
*/
static class PostOpenDeployTasksThread extends Thread {
private Exception exception = null;
private final Server server;
private final RegionServerServices services;
private final HRegion region;
private final AtomicBoolean signaller;
PostOpenDeployTasksThread(final HRegion region, final Server server,
final RegionServerServices services, final AtomicBoolean signaller) {
super("PostOpenDeployTasks:" + region.getRegionInfo().getEncodedName());
this.setDaemon(true);
this.server = server;
this.services = services;
this.region = region;
this.signaller = signaller;
}
public void run() {
try {
this.services.postOpenDeployTasks(this.region,
this.server.getCatalogTracker());
} catch (Exception e) {
LOG.warn("Exception running postOpenDeployTasks; region=" +
this.region.getRegionInfo().getEncodedName(), e);
this.exception = e;
}
// We're done. Set flag then wake up anyone waiting on thread to complete.
this.signaller.set(true);
synchronized (this.signaller) {
this.signaller.notify();
}
}
/**
* @return Null or the run exception; call this method after thread is done.
*/
Exception getException() {
return this.exception;
}
}
/**
* @param r Region we're working on.
* @return whether znode is successfully transitioned to OPENED state.
* @throws IOException
*/
private boolean transitionToOpened(final HRegion r) throws IOException {
boolean result = false;
HRegionInfo hri = r.getRegionInfo();
final String name = hri.getRegionNameAsString();
// Finally, Transition ZK node to OPENED
try {
if (ZKAssign.transitionNodeOpened(this.server.getZooKeeper(), hri,
this.server.getServerName(), this.version) == -1) {
LOG.warn("Completed the OPEN of region " + name +
" but when transitioning from " +
" OPENING to OPENED got a version mismatch, someone else clashed " +
"so now unassigning -- closing region on server: " +
this.server.getServerName());
} else {
LOG.debug("region transitioned to opened in zookeeper: " +
r.getRegionInfo() + ", server: " + this.server.getServerName());
result = true;
}
} catch (KeeperException e) {
LOG.error("Failed transitioning node " + name +
" from OPENING to OPENED -- closing region", e);
}
return result;
}
/**
* This is not guaranteed to succeed, we just do our best.
* @param hri Region we're working on.
* @return whether znode is successfully transitioned to FAILED_OPEN state.
*/
private boolean tryTransitionFromOpeningToFailedOpen(final HRegionInfo hri) {
boolean result = false;
final String name = hri.getRegionNameAsString();
try {
LOG.info("Opening of region " + hri + " failed, transitioning" +
" from OPENING to FAILED_OPEN in ZK, expecting version " + this.version);
if (ZKAssign.transitionNode(
this.server.getZooKeeper(), hri,
this.server.getServerName(),
EventType.RS_ZK_REGION_OPENING,
EventType.RS_ZK_REGION_FAILED_OPEN,
this.version) == -1) {
LOG.warn("Unable to mark region " + hri + " as FAILED_OPEN. " +
"It's likely that the master already timed out this open " +
"attempt, and thus another RS already has the region.");
} else {
result = true;
}
} catch (KeeperException e) {
LOG.error("Failed transitioning node " + name +
" from OPENING to FAILED_OPEN", e);
}
return result;
}
/**
* Try to transition to open. This function is static to make it usable before creating the
* handler.
*
* This is not guaranteed to succeed, we just do our best.
*
* @param rsServices
* @param hri Region we're working on.
* @param versionOfOfflineNode version to checked.
* @return whether znode is successfully transitioned to FAILED_OPEN state.
*/
public static boolean tryTransitionFromOfflineToFailedOpen(RegionServerServices rsServices,
final HRegionInfo hri, final int versionOfOfflineNode) {
boolean result = false;
final String name = hri.getRegionNameAsString();
try {
LOG.info("Opening of region " + hri + " failed, transitioning" +
" from OFFLINE to FAILED_OPEN in ZK, expecting version " + versionOfOfflineNode);
if (ZKAssign.transitionNode(
rsServices.getZooKeeper(), hri,
rsServices.getServerName(),
EventType.M_ZK_REGION_OFFLINE,
EventType.RS_ZK_REGION_FAILED_OPEN,
versionOfOfflineNode) == -1) {
LOG.warn("Unable to mark region " + hri + " as FAILED_OPEN. " +
"It's likely that the master already timed out this open " +
"attempt, and thus another RS already has the region.");
} else {
result = true;
}
} catch (KeeperException e) {
LOG.error("Failed transitioning node " + name + " from OFFLINE to FAILED_OPEN", e);
}
return result;
}
/**
* @return Instance of HRegion if successful open else null.
*/
HRegion openRegion() {
HRegion region = null;
try {
// Instantiate the region. This also periodically tickles our zk OPENING
// state so master doesn't timeout this region in transition.
region = HRegion.openHRegion(this.regionInfo, this.htd,
this.rsServices.getWAL(this.regionInfo),
this.server.getConfiguration(),
this.rsServices,
new CancelableProgressable() {
public boolean progress() {
// We may lose the znode ownership during the open. Currently its
// too hard interrupting ongoing region open. Just let it complete
// and check we still have the znode after region open.
return tickleOpening("open_region_progress");
}
});
} catch (Throwable t) {
// We failed open. Our caller will see the 'null' return value
// and transition the node back to FAILED_OPEN. If that fails,
// we rely on the Timeout Monitor in the master to reassign.
LOG.error(
"Failed open of region=" + this.regionInfo.getRegionNameAsString()
+ ", starting to roll back the global memstore size.", t);
// Decrease the global memstore size.
if (this.rsServices != null) {
RegionServerAccounting rsAccounting =
this.rsServices.getRegionServerAccounting();
if (rsAccounting != null) {
rsAccounting.rollbackRegionReplayEditsSize(this.regionInfo.getRegionName());
}
}
}
return region;
}
void cleanupFailedOpen(final HRegion region) throws IOException {
if (region != null) region.close();
}
private boolean isRegionStillOpening() {
byte[] encodedName = regionInfo.getEncodedNameAsBytes();
Boolean action = rsServices.getRegionsInTransitionInRS().get(encodedName);
return Boolean.TRUE.equals(action); // true means opening for RIT
}
/**
* Transition ZK node from OFFLINE to OPENING.
* @param encodedName Name of the znode file (Region encodedName is the znode
* name).
* @param versionOfOfflineNode - version Of OfflineNode that needs to be compared
* before changing the node's state from OFFLINE
* @return True if successful transition.
*/
boolean transitionZookeeperOfflineToOpening(final String encodedName,
int versionOfOfflineNode) {
// TODO: should also handle transition from CLOSED?
try {
// Initialize the znode version.
this.version = ZKAssign.transitionNode(server.getZooKeeper(), regionInfo,
server.getServerName(), EventType.M_ZK_REGION_OFFLINE,
EventType.RS_ZK_REGION_OPENING, versionOfOfflineNode);
} catch (KeeperException e) {
LOG.error("Error transition from OFFLINE to OPENING for region=" +
encodedName, e);
this.version = -1;
return false;
}
boolean b = isGoodVersion();
if (!b) {
LOG.warn("Failed transition from OFFLINE to OPENING for region=" +
encodedName);
}
return b;
}
/**
* Update our OPENING state in zookeeper.
* Do this so master doesn't timeout this region-in-transition.
* @param context Some context to add to logs if failure
* @return True if successful transition.
*/
boolean tickleOpening(final String context) {
if (!isRegionStillOpening()) {
LOG.warn("Open region aborted since it isn't opening any more");
return false;
}
// If previous checks failed... do not try again.
if (!isGoodVersion()) return false;
String encodedName = this.regionInfo.getEncodedName();
try {
this.version =
ZKAssign.retransitionNodeOpening(server.getZooKeeper(),
this.regionInfo, this.server.getServerName(), this.version);
} catch (KeeperException e) {
server.abort("Exception refreshing OPENING; region=" + encodedName +
", context=" + context, e);
this.version = -1;
return false;
}
boolean b = isGoodVersion();
if (!b) {
LOG.warn("Failed refreshing OPENING; region=" + encodedName +
", context=" + context);
}
return b;
}
private boolean isGoodVersion() {
return this.version != -1;
}
}